Hydrologists and Floodplain Managers don't like to hear a term like "100-year flood" because, scientifically, it is a misinterpretation of terminology that leads to a misconception of what a 100-year flood really is.
Instead of the term "100-year flood" we would rather describe this hydrologic event as a flood having a 100-year recurrence interval. In other words, a flood of that magnitude has a 1 percent chance of happening in any year.